Controlled pressure release for packaged batteries and associated systems and methods

ABSTRACT

A battery package for providing power to an electronic device is described herein. In one embodiment, the battery package includes a casing configured to enclose at least one battery cell. The casing includes a wall having an internal surface, an external surface and a dimple. The dimple extends outward from the internal surface to an intermediate section of the wall. In a particular embodiment, the dimple is positioned to rupture under high pressure conditions and direct escaping gases away from selected components of the electronic device in which the battery package is housed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/956,288 filed Aug. 16, 2007, entitled “CONTROLLEDPRESSURE RELEASE FOR PACKAGED BATTERIES AND ASSOCIATED SYSTEMS ANDMETHODS,” which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to packaged battery devices andmethods of manufacturing such devices.

BACKGROUND

Many portable electronic devices employ a battery package in lieu ofconventional batteries or conventional battery arrangements. Existingbattery packages are rechargeable and customizable, and typicallyinclude an array of rechargeable battery cells, circuitry for monitoringand regulating output power, and a casing that houses the battery cellsand battery circuitry. Accordingly, battery packages can be tailored sothat the battery cells meet specific power requirements, the packagecircuitry provides power feedback and control, and the package casingprotects the package cells and circuitry from various environmentalfactors. For example, battery cells for portable medical equipment(e.g., defibrillators, portable X-ray devices, and infusion pumps) aredesigned to meet stringent power tolerances. The package circuitries forhand-held data collection devices (e.g., barcode scanners, RFID readers,and portable printers) are configured to accommodate usage patterns, andthe package casings for field instruments have contact openings that arefitted with Gore-Tex® seals to prevent moisture from entering thebattery package.

Despite the foregoing advantages, battery packages are more complex thanconventional batteries and can therefore be more prone to failure ordiminishing performance. For example, if an individual battery cellfails, this event can cause other battery cells within the package torapidly discharge, resulting in overheating. If the package circuitryfails, the battery package may stop functioning correctly. If thepackage casing becomes compromised, moisture or other types ofenvironmental influences may affect battery package performance. Thus,to facilitate battery package operation, battery package designers needto address issues that are not common to conventional batteries andbattery arrangements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a portable device and a battery packageconfigured in accordance with one embodiment of the disclosure.

FIG. 2A is cross-sectional end view of the battery package of FIG. 1.

FIG. 2B is a cross-sectional side view of the battery package of FIG. 1.

FIG. 2C is an isometric view of an interior portion of the batterypackage of FIG. 1.

FIG. 3 is an isometric view of a portion of an interior surface of apackage casing having an arrangement of dimples in accordance withanother embodiment of the disclosure.

FIG. 4 is a cross-sectional view of a package casing in accordance withanother embodiment of the disclosure.

FIG. 5 is a cross-sectional side view of a dimple extending into apackage casing in accordance with an embodiment of the disclosure.

FIG. 6 is a cross-sectional side view of a dimple extending into apackage casing in accordance with another embodiment of the disclosure.

FIG. 7 is an isometric view of a portion of an interior surface of apackage casing having an arrangement of grooves in accordance withanother embodiment of the disclosure.

DETAILED DESCRIPTION

Several aspects of the present disclosure are directed to devices andmethods for releasing pressure from packaged battery devices in acontrolled fashion, for example in a controlled direction. Well-knowncharacteristics often associated with these devices and methods have notbeen shown or described in detail to avoid unnecessarily obscuring thedescription of the various embodiments. Those of ordinary skill in therelevant art will understand that additional embodiments may bepracticed without several of the details described below, and that otherembodiments may include aspects in addition to those described below.

FIG. 1 is an isometric view of a representative embodiment of a batterypackage 100 that can be operably coupled to a portable device 105. Thebattery package 100 can include a package casing or shell 120 (e.g.,made from molded plastic) that houses one or more battery cells. Thecasing 120 can further include an internally located dimple 140, blindhole, cavity or other surface depression that extends from an opening inan interior surface of the casing 120 to an intermediate section of thecasing 120. The dimple 140 is generally concealed by an exterior surfaceof the casing 120 (i.e., the dimple 140 is not visible from the exteriorsurface of the casing 120). The portable device 105 can have a housingbody 106 that includes external electronic components 108 (e.g., an LEDdisplay and related controls) accessible from an exterior surface of thehousing body 106, and internal electronic components 109 (e.g., aprinted circuit board, a microelectronic chip, a wire or related signalpath, and/or other types of electronic circuitry) disposed within thehousing body 106. When the battery package 100 is coupled to providepower to the portable device 105, the dimple 140 is arranged so that itextends in a direction that generally faces away from the electroniccomponents 108-109 and/or other selected portions of the portable device105. In other embodiments, the dimple 140 can also be arranged to faceaway from neighboring devices, e.g., other portable devices locatedexternal to the case 120.

In a particular embodiment, the package casing 120 allows internalpressures within the casing to be preferentially released and/orequalized at the dimple 140. The dimple 140 can accordingly beconfigured to be a local weak point in the casing wall that is the firstto rupture in the event of a rapid pressure accumulation, such as from abattery cell out-gassing. Battery cell out-gassing or venting can occurwhen a battery cell is exposed to abusive conditions, and generallyresults in the emission of gas or vapor. Large amounts of emitted gascan accumulate within the package casing 120, creating a pressuredifferential at the casing walls. If the pressure differential issufficiently large, the package casing 120 will preferentially ruptureat the dimple 140. The dimple 140 can be positioned so that the escapinggases are directed along a selected vector (e.g., away from selectedfeatures) and can therefore mitigate potential damage to the portabledevice 105 or portions of the device (e.g., the electronic components108-109).

Unlike conventional battery packages, embodiments of the package casing120 are equipped to release internally accumulated pressure in apredetermined direction. When undergoing a large pressure differential,conventional battery packages tend to rupture at one or more weak pointsthat may be located randomly in the casing walls, which creates a riskfor damage to the portable device in which the battery package ishoused. It is generally difficult to design pressure release mechanismsinto conventional package casings because such casings should generallybe well-sealed. For example, some pressure release mechanisms include anopening with a membrane (made of a material different than that of thecasing wall) positioned over or across the opening. Such membranes canbe expensive, due to the cost of the membrane material and itsinstallation, and they do not always interface well with package casingmaterial. Accordingly, conventional package casings generally rupture inan uncontrolled manner and/or at uncontrolled locations in the casing.By contrast, embodiments of the dimple 140 are designed to directrupture gases away from the package casing 120 at a predeterminedlocation and/or in a predetermined direction selected to control, and insome cases eliminate, potential damage to system components.Furthermore, because the dimple 140 does not extend all the way throughthe casing walls, the release mechanism does not require a secondarymaterial. Instead, in particular embodiments, the package casing 120 canbe made from a single homogenous material and the dimple 140 may be madeas part of the process of molding the package casing 120. The dimple 140can also be concealed inside the package casing 120, which can providefor an aesthetically pleasing outward appearance. Further, the dimple140 can allow the battery package 100 to be used in submersibleapplications and yet also have a pressure release mechanism.Conventional membrane materials (such as Gore-Tex®) are typicallyattached to the wall of a battery package casing through the use ofadhesives. Such attachments can be compromised during immersion inliquid, allowing the ingress of liquid into the battery package casing.However, unlike a membrane opening, the dimple 140 does not exposeinternal elements of the package casing 120 to the outside environment.Thus, when the package casing 120 is submersed, liquid cannot easilypenetrate the casing and damage electrical components internal to thecasing.

As previously described, in particular embodiments, before any ruptureoccurs in the package casing 120, the dimple 140 is not visible from theexterior of the package casing 120. When a rupture occurs in the packagecasing 120 at the location of the dimple 140, it can be seen on theexterior of the package casing 120. Because such a rupture is visible,it can be easily ascertained from a visual inspection of the exterior ofthe package casing 120. Accordingly, such a visual inspection enables auser to determine whether there was a prior accumulation of pressurewithin the package casing 120 and subsequent release of pressure throughthe package casing 120 at the dimple 140. Accordingly, embodiments ofthe dimple 140 enable the user to easily diagnose problems with batterycells 160 within the package casing 120. Because such ruptures wouldtypically impair the integrity of the package casing 120, embodiments ofthe dimple 140 can be thought of as single-use, i.e., allowing a singleinstance of pressure release before repair or replacement of the packagecasing 120 is necessitated. In contrast, conventional membrane openingswould allow for multiple instances of pressure release before requiringrepair or replacement of the casings carrying them.

Also as previously described, because embodiments of the dimple 140 donot extend all the way through the package casing 120, the packagecasing 120 has a smooth exterior surface. This may enable an easier ormore straightforward manufacturing process for the package casing 120,because there may be no need to form an opening through the packagecasing 120 and attach a valve or conventional membrane opening, as aprocess for manufacturing a casing having a conventional membraneopening typically would require. Another advantage of a package casing120 having a smooth exterior surface is that because a user can easilyclean it or wipe it down, the user may more easily maintain portabledevices 105 with such package casings 120.

FIG. 2A is a more detailed end view of the battery package 100, showingan embodiment of the package casing 120 having two or more portionsjoined at a casing seal 130. The package casing 120 may comprise avariety of plastic materials, e.g., polyvinyl chloride, polyethylene,polymethyl methacrylate and/or other acrylics, silicones, and/orpolyurethanes. The casing seal 130 may be an ultrasonic weld or otherfastening arrangement that holds the casing body together, creating aninternal cavity within the package casing 120. The seal 130 is generallystronger than the casing wall at the dimple 140. The dimple 140 extendsa fixed depth into the casing wall and it may be adjacent to one or moreof the battery cells 160. The battery cells 160 generally compriserechargeable chemistries, e.g., lithium-ion, nickel-metal-hydride,nickel-iron, and/or nickel-cadmium.

FIG. 2B is a cross-sectional side view of an embodiment of the batterypackage 100 showing the package casing 120, the casing seal 130, thedimple 140, the battery cells 160, and package interconnects 180 andpackage circuitry 190 coupled to the battery cells 160. The packageinterconnects 180 electrically couple the battery package 100 to theportable device 105 (FIG. 1) and the package circuitry 190 mayoptionally add power feedback and control functionality to the batterypackage 100.

FIG. 2C is an isometric view of an interior portion of an embodiment ofthe package casing 120. The casing 120 can include a casing wall 122having an interior surface 126 and an exterior surface 128 separatedfrom the interior surface 126 by a thickness t₁. The dimple 140 can belocated at the interior surface 126 and can have a diameter width, orcross-sectional dimension d₁ and a fixed depth or height d₂. Inparticular embodiments, the dimple diameter d₁ and depth d₂ can beinversely proportional to the strength (e.g., shear strength and/ordeformation resistance) of the casing wall 122 at the dimple 140.Accordingly, a variety of design considerations may be evaluated todetermine an appropriate size of the dimple 140 so that itpreferentially ruptures at a preselected pressure and/or in apreselected direction. Such design considerations include the interiorvolume or interior space of the package casing 120, the casing wallthickness t₁, as well as the presence of other local weak points withinthe casing 120 (e.g., corners, seal regions, casing defects, and/orother features). In a particular embodiment the casing wall thickness t₁can be in the range of from about 0.04 inches to about 0.06 inches andthe dimple depth d₂ can be in the range of from about 0.005 to about0.03 inches.

In an embodiment shown in FIG. 2C, the dimple 140 is a singlecylindrically shaped hole in the casing wall 122. The dimple 140includes at least one sidewall 144 extending from an opening 142 in theinterior surface to an intermediate section 146 of the casing wall 122.In other embodiments, more than one dimple may be made in the casingwall at one or more locations within the package casing. For example,FIG. 3 is an isometric view of a representative casing wall 322 havingan interior surface 326 and a plurality of dimples 340 extending from aplurality of openings (not labeled in FIG. 3) in the interior surface326 into intermediate sections (not labeled in FIG. 3) of the casingwall 322. At least some of the dimples 340 are proximate to each other.FIG. 4 is a cross-sectional view of a representative package casing 400having a dimple 442 located at a casing end wall 425 and a plurality ofdimples 444 located at a casing top wall 427. The casing end wall 425and the casing top wall 427 are adjacent to each other. The dimplearrangements of FIGS. 3 and 4 can distribute the gases from a packagecasing rupture across extended portions of one or more casing walls.This in turn can reduce the escape velocity of the gases, while stillkeeping the gases away from selected components of the portable devicein which the package casing is positioned.

In other embodiments, the dimple may have a base 523 and other shapes orprofiles. For example, FIG. 5 is a cross-sectional view of casing wall522 with a dimple 540 that has a base 523 and sloping surfaces 521 orsidewalls. The sloping surfaces 521 extend to the base 523 by divergingfrom an opening (not labeled in FIG. 5) to the base 523. The angle ofthe sloping surfaces 521 may be selected so as to fan out the gases asthey are ejected or expelled along the sloping surfaces 521 through arupture in the casing wall 522 at the dimple 540. As a result, thesloping surfaces 521 can reduce the escape velocity and the density ofthe gases as they are emitted through a rupture in the casing wall 522at the dimple 540.

FIG. 6 is a cross-sectional view of a casing wall 622 having a dimple640 with trench regions 621 formed at a base 623 of the dimple 640. Thebase 623 has sidewalls 644 that extend by converging forward from anintermediate section 646 of the casing wall to a second intermediatesection 648 of the casing wall. It is expected that when the dimple 640ruptures, the configurations of the trench regions 621 will cause thedimple 640 to rupture completely or partially in a manner that issimilar to opening a can of soda. As a result, the base 623 is expectedto completely or partially break away from the casing wall 622. Theresulting opening and/or deformed base 623 can provide a visibleindication that the casing wall 622 has ruptured.

In other embodiments, the dimple can have any of a variety of othertypes of sharp, angled, curved, or rounded hole-type shapes.Additionally, in lieu of a hole-type shape, a general surface depressionmay be molded, scribed, keyed, or otherwise formed into the surface of acasing wall. For example, FIG. 7 is an isometric view of a portion of acasing wall 722 having an interior surface 726 that includes a pluralityof intersecting grooves 742 or scored notches. The pressure at which thecasing wall 722 ruptures can be controlled by controlling the densityand/or the depth of the grooves 742. In general, the deeper and/orlarger a surface depression is, the easier it is to rupture a packagecasing at the surface depression.

Dimples, blind holes, and/or other type of surface depressions includingthose described above can be manufactured using a variety of suitabletechniques. For example, in many embodiments, one or more dimples can bedesigned into a mold that is used for forming the package casing.Accordingly, the dimples are formed concurrently with the packagecasing. In other embodiments, a dimple can be made in a separatemanufacturing step. For example, dimples can be formed using a drill, astamping tool, a laser, a waterjet, a scribe, or other type ofinstrument that removes and/or deforms the material forming the casingwall.

From the foregoing, it will be appreciated that specific, representativeembodiments have been described herein for purposes of illustration, butthat various modifications may be made to these embodiments. Forexample, the package casings can have characteristics other than thosespecifically described above, including screws to hold the shelltogether, a combination of materials other than plastics (e.g., metals),and a shape that is suited to fit within or couple to a particular typeof electronic device. The battery packages can also have features otherthan those described above and shown in the Figures and may also includemore or fewer components than those illustrated. For example, in someembodiments the package circuitry may be omitted. In many embodiments adifferent number of battery cells may be housed in variously sizedpackages, and in other embodiments the battery cells may comprisenon-rechargeable chemistries. While not expressly shown in the Figures,the battery package and corresponding package casing can be coupled toany of a wide variety of portable and stationary electronic devices.While representative examples of pressure release points were describedabove in the content of dimples, other embodiments may include othertypes of depressions or features. In addition, the dimples, blind holes,cavities and other surface depressions may be configured in mannersother than those specifically shown and described above so that thepackage casing preferentially ruptures in a manner that mitigates damageto internal components, neighboring devices, or other objects that arewithin the vicinity of the package casing. Further, while advantagesassociated with certain embodiments have been described in the contextof those embodiments, other embodiments may also exhibit suchadvantages, and not all embodiments need necessarily exhibit suchadvantages to fall within the scope of the invention. Accordingly, theinvention is not limited except as by the appended claims.

1. A battery package for providing power to an electronic device, thebattery package comprising a casing configured to enclose at least onebattery cell, wherein the casing includes a wall having an internalsurface, an external surface and a dimple extending outward from theinternal surface to an intermediate section of the wall.
 2. The batterypackage of claim 1 wherein the dimple is not visible from the externalsurface.
 3. The battery package of claim 1 wherein the electronic devicehas an electronic component, and wherein the dimple extends outward in adirection generally facing away from the electronic component.
 4. Thebattery package of claim 1 wherein the dimple is generally cylindrical.5. The battery package of claim 1 wherein the wall has a thickness ofapproximately 0.04 inches to approximately 0.06 inches and the dimplehas a depth of approximately 0.005 inches to approximately 0.03 inches.6. The battery package of claim 1 wherein the casing forms an internalvolume, the wall has a thickness, the dimple has a depth and across-sectional dimension, and wherein at least one of the depth and thecross-sectional dimension are determined based at least partially uponat least one of the internal volume and the wall thickness.
 7. Thebattery package of claim 1 wherein the dimple is a first dimpleextending from a first portion of the internal surface to a firstintermediate section of the wall, and wherein the casing furtherincludes a second dimple extending from a second portion of the internalsurface to a second intermediate section of the wall.
 8. The batterypackage of claim 7 wherein the first and second dimples are proximate toeach other.
 9. The battery package of claim 1 wherein the wall is afirst wall having a first internal surface, a first external surface anda first dimple extending from the first internal surface to a firstintermediate section of the first wall, and wherein the casing furtherincludes a second wall having a second internal surface, a secondexternal surface and a second dimple extending from the second internalsurface to a second intermediate section of the second wall.
 10. Thebattery package of claim 9 wherein the first and second walls areadjacent to each other.
 11. The battery package of claim 1 wherein thedimple includes a sidewall diverging outward from the internal surfaceto the intermediate section.
 12. The battery package of claim 1 whereinthe intermediate section is a first intermediate section, and whereinthe dimple has a base having a sidewall converging inward from theintermediate section to a second intermediate section of the wall. 13.The battery package of claim 1 wherein the dimple includes at least twosidewalls converging outward from the internal surface to theintermediate section of the wall.
 14. A casing for housing at least onebattery cell, the casing comprising walls forming an interior space, atleast one wall including at least one opening, and a cavity including asidewall extending outward from the at least one opening to anintermediate section of the at least one wall, wherein the portion ofthe at least one wall from the intermediate section to an externalsurface of the casing is configured to rupture when the interior spaceis subjected to an elevated internal pressure.
 15. The casing of claim14, wherein the sidewall diverges rearward from the at least one openingto the intermediate section of the at least one wall.
 16. An electronicdevice, comprising: a housing; an electronic component positioned withinthe housing; and a battery package positioned within the housing andelectrically coupled to the electronic component, the battery packageincluding a casing enclosing at least one battery cell, wherein thecasing includes a wall having an internal surface, an external surfaceand a dimple extending outward from the internal surface to anintermediate section of the wall, and wherein the dimple extends outwardin a direction generally facing away from the electronic component. 17.The electronic device of claim 16, wherein 7 the dimple includes asidewall diverging outward from the internal surface to the intermediatesection
 18. A method for manufacturing a battery package casing, themethod comprising: forming at least one blind hole at an interiorsurface of the battery package casing, wherein the blind hole extendsfrom the interior surface to an intermediate section of the batterypackage casing; disposing a battery cell within the battery packagecasing; and sealing the battery package casing.
 19. The method of claim18, wherein the blind hole has a depth and a cross-sectional dimension,and wherein forming the at least one blind hole at the interior surfaceof the battery package casing includes forming the depth and thecross-sectional dimension of the blind hole so as to cause the portionof the battery package casing from the intermediate section to anexterior surface of the battery package casing to rupture when aninterior pressure of the battery package casing reaches a preselectedpressure.
 20. The method of claim 18, further comprising forming thebattery package casing, and wherein forming the at least one blind holeat the interior surface of the battery package casing includes formingthe at least one blind hole at the interior surface of the batterypackage casing concurrently with forming the battery package casing. 21.The method of claim 18, further comprising forming the battery packagecasing, and wherein forming the at least one blind hole at the interiorsurface of the battery package casing includes removing material fromthe battery package casing to form the at least one blind hole.
 22. Themethod of claim 18, further comprising forming the battery packagecasing, and wherein forming the at least one blind hole at the interiorsurface of the battery package casing includes forming the at least oneblind hole without removing material from the battery package casing.23. The method of claim 18, wherein the blind hole has a depth and across-sectional dimension, wherein the portion of the battery packagecasing between the intermediate section of the wall and an externalsurface of the battery package casing has a strength, and whereinforming the at least one blind hole at the interior surface of thebattery package casing includes selecting at least one of the blind holedepth and the blind hole cross-sectional dimension based at leastpartially upon an inverse relationship to the strength of the portion ofthe battery package casing between the intermediate section of the walland an external surface of the battery package casing.
 24. A method forutilizing a battery package casing, the method comprising: providing acasing having at least one blind hole disposed at an interior surface ofthe casing, wherein the casing houses a battery; and equalizing abattery-induced pressure accumulation in the casing by rupturing thecasing at the blind hole.
 25. The method of claim 24 wherein providing acasing having at least one blind hole includes providing a casing havinga blind hole having dimensions configured so as to cause the casing atthe blind hole to be the first portion of the casing to rupture whenequalizing a battery-induced pressure accumulation in the casing. 26.The method of claim 24 wherein providing a casing having at least oneblind hole includes providing a casing having a blind hole having asidewall diverging from the interior surface to an intermediate sectionof the casing, and wherein equalizing a battery-induced pressureaccumulation in the casing includes expelling accumulated gases in thecasing along the diverging sidewall and through the rupture in thecasing at the blind hole.
 27. The method of claim 24, wherein equalizinga battery-induced pressure accumulation in the casing by rupturing thecasing at the blind hole includes preferentially directing accumulatedgases in the casing through the rupture in the casing at the blind holeand away from an electronic component of an electronic device to whichthe battery package casing is operably coupled.